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Quasi-equilibrium closure hierarchies for the Boltzmann equation

Quasi-equilibrium closure hierarchies for the Boltzmann equation
Quasi-equilibrium closure hierarchies for the Boltzmann equation
In this paper, explicit method of constructing approximations (the triangle entropy method) is developed for nonequilibrium problems. This method enables one to treat any complicated nonlinear functionals that fit best the physics of a problem (such as, for example, rates of processes) as new independent variables. The work of the method is demonstrated on the Boltzmann's-type kinetics. New macroscopic variables are introduced (moments of the Boltzmann collision integral, or scattering rates). They are treated as independent variables rather than as infinite moment series. This approach gives the complete account of rates of scattering processes. Transport equations for scattering rates are obtained (the second hydrodynamic chain), similar to the usual moment chain (the first hydrodynamic chain). Various examples of the closure of the first, of the second, and of the mixed hydrodynamic chains are considered for the hard sphere model. It is shown, in particular, that the complete account of scattering processes leads to a renormalization of transport coefficients. The method gives the explicit solution for the closure problem, provides thermodynamic properties of reduced models, and can be applied to any kinetic equation with a thermodynamic Lyapunov function.
entropy, MaxEnt, kinetics, Boltzmann equation, Fokker–Planck equation, model reduction
0378-4371
325-364
Gorban, Alexander N.
31914661-757a-4b6b-a953-109ac7499746
Karlin, Iliya V.
3331716f-692a-4b81-87a4-9aad489d025d
Gorban, Alexander N.
31914661-757a-4b6b-a953-109ac7499746
Karlin, Iliya V.
3331716f-692a-4b81-87a4-9aad489d025d

Gorban, Alexander N. and Karlin, Iliya V. (2006) Quasi-equilibrium closure hierarchies for the Boltzmann equation. Physica A: Statistical Mechanics and its Applications, 360 (2), 325-364. (doi:10.1016/j.physa.2005.07.016).

Record type: Article

Abstract

In this paper, explicit method of constructing approximations (the triangle entropy method) is developed for nonequilibrium problems. This method enables one to treat any complicated nonlinear functionals that fit best the physics of a problem (such as, for example, rates of processes) as new independent variables. The work of the method is demonstrated on the Boltzmann's-type kinetics. New macroscopic variables are introduced (moments of the Boltzmann collision integral, or scattering rates). They are treated as independent variables rather than as infinite moment series. This approach gives the complete account of rates of scattering processes. Transport equations for scattering rates are obtained (the second hydrodynamic chain), similar to the usual moment chain (the first hydrodynamic chain). Various examples of the closure of the first, of the second, and of the mixed hydrodynamic chains are considered for the hard sphere model. It is shown, in particular, that the complete account of scattering processes leads to a renormalization of transport coefficients. The method gives the explicit solution for the closure problem, provides thermodynamic properties of reduced models, and can be applied to any kinetic equation with a thermodynamic Lyapunov function.

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More information

Submitted date: 31 January 2005
Published date: 1 February 2006
Keywords: entropy, MaxEnt, kinetics, Boltzmann equation, Fokker–Planck equation, model reduction

Identifiers

Local EPrints ID: 49240
URI: http://eprints.soton.ac.uk/id/eprint/49240
ISSN: 0378-4371
PURE UUID: afab4bb7-ad7f-42d9-88c2-19737f523b34

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Date deposited: 25 Oct 2007
Last modified: 15 Mar 2024 09:54

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Contributors

Author: Alexander N. Gorban
Author: Iliya V. Karlin

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